Backward Support for Swift

Support existing client functionality including GET /v1.0 to get a token and returning URLs to clients so they know where to go to get their data.

We're proposing the following as an approach:
1. Auth 1.0/1.1 compatible calls will be implemented as a WSGI component on Keystone
2. The BaseURLs will be translated to X-Storage-URL (and other 1.0 compatible headers) using settings in a conf file for the WSGI component.
3. Authorization (token generation, etc...) will be performed by the core 2.0 API and routed to it by the WSGI layer (i.e. no duplication of token generation code within WSGI component)
4. Auth 1.0 and 1.1 compatibility will be released for the public API only to support existing tooling.
5. We will rename folders in Keystone to the following:

auth_protocols will changed to `middleware` and will host middleware for use with other services.
backends will be created for back-end components (sqlite, ldap, etc...)
frontends will be added and will host frontends for Keystone (including the Auth 1.0/1.1 WSGI component)